Metallizing solution for intensifying layers of metallic, imaged nuclei

ABSTRACT

Form metal layer of a metal such as copper, tin, nickel or cobalt on an electrically nonconducting layer by first forming a silver or mercury nuclei image on the layer and then treating the layer with an aqueous solution of the metal to be deposited and a mixture of reducing metal ions and the oxidated forms thereof. An example is an aqueous solution of nickel ions and mixture of Cr2 and Cr3. This abstract is not intended to be a description of the invention defined by the claims.

United States Patent De Ruig et al. 1 Jan. 25, 1972 METALLIZING SOLUTION FOR 1 R ferences Cited ii ffiiifiifii fii fm v 2,662,0l4 12/1953 Umberger ..95/88 [72] Inventors: Willem Gerbreeht De iz, Tromplaan; 3,379,539 4/1968 McGrath et al ..l 17/130 Arian Molenaar; Hendrik Junker, both of Emm ing l, Eindhoven, 0f Nethef- Primary Examiner-Norman G. Torchin lands Assistant Examiner-Edward C. Kimlin [73] Assignee: U.S. Philips Corporation, New York, NY. A"0mey Frank Tnfan [22] Filed: May 2, 1967 [57] ABSTRACT [21] Appl. No.: 635,409 Form metal layer of a metal such as copper, tin, nickel or cobalt on an electrically nonconducting layer by first forming a silver or mercury nuclei image on the layer and then treating [52] US. Cl the layer with an aqueous solution of the meta] m be deposited Int. Cl and a mixture of reducing metal ions and the oxidated forms Field of Search ..96/60, 50, 63, 66; l l7/l 30, ll'l/l30E,l60

thereof. An example is an aqueous solution of nickel ions and mixture of Cr and Cr. This abstract is not intended to be a description of the invention defined by the claims.

4 Claims, No'Drawings METALLIZING SOLUTION FOR INTENSIFYING LAYERS OF METALLIC, IMAGED NUCLEI The invention relates to a metallizing solution formed by a primarily aqueous solution containing metal ions and a reducmetal on the latent image. Metal nuclei may be obtained, for example, by a known photographic method in which a light-sensitive compound is used from which a light-reaction product is formed upon exposure, said product being capable of separating mercury or silver fonner then acting as a reducing agent.

In general, it has not physical developers are sensitizing of the surface, for example, by treating it with a hydrochloric acid stannous chloride solution, followed by a This method is not very interesting; it is not only fairly circuitous, but it also requires a comparatively thick layer of silver or of another noble metal, sometimes up to a thickness of 1,000 A., in order to ensure adequately rapid deposition of copper, nickel or cobalt. In many electrotechnical uses, particularly in the field of printed wiring for professional and military purposes the presence of such quantities of silver is prohibitive, since at the operational temperature silver may migrate and thus produce unwanted effects. Palladium and platinum have the disadvantage that they are too expensive for large scale use.

The invention which other metals less noble than mercury, um.

The metallizing solution according to the invention and formed but nobler than cadminoble than mercury, as well as reducing may be present in different valencies, the latter ions forming, together with the ions formed therefrom by oxidation, a reversible mixture, whose normal reduction-oxidation potential is less than 780 mv., while the relevant metal to be deposited therefrom with respect to its ions from the reduction-oxidation potential of the reversible ion mixture has a positive value. More specifically the concentrations of the ions being such that the difference means of the metallizing bath according to the invention are: copper, lead, tin, nickel, cobalt and indium. Also thallium, molybdenum and germanium can be deposited, if the availability and the solubility of the salts and the compatibility thereof with the redox mixture are not likely to give rise to difficulties,

The reduction giving rise to deposition of the aforesaid metals is carried out by means of the reducing components of reversible, inorganic redox systems, whose normal reductionoxidation potential lies between 430 mv. and 780 mv. Among those are the redox systems: Fe /Fe*; VWVO; :s+ joz+; vm; Tim/Tim; z+ 3+;' w 3+ The couple of Sn /Sn does not behave in a reversible manner and therefore Sn cannot be used for the reduction for deposition of the aforesaid metals.

The difference between the potential of the metal to be tively high, for example, 400 mv.,

and fogging may be a source of trouble for certain uses. Considering the Nemst equation for the reduction of bivalent metal ions:

wherein E, designates the relevant normal potentials and a the activities of the relevant ions, it will be obvious that by adding raised by adding a complex former reducing mainly a,,

It is thus even possible to reduce cupric ions in an alkaline solution while employing triethanolamine or the sodium salt of ethylene diamine tetra-acetic acid as a complex former, by means of ferric ions, be it that the rate of deposition is restricted by the limit to which the concentration of the ferrous salt is subjected on account of the formation of precipitate.

Surprisingly no preliminary catalyzing of the nuclear metal images is required with the use of the type of metallizing solutions according to the invention. As compared with the known methods of producing images of the metals concerned this method is therefore less elaborate and less expensive.

The images obtained by means of the metallizing solutions according to-the invention, consisting of lead or tin, may be employed in the manufacture of cryotron elements, that is to say, elements in which an usability in cryotron elements. Lead or tin images obtained by means of the metallizing baths according to the invention have properties suitable for these uses without the need for further treatment.

Thin cobalt and nickel layers obtained by means of the metallizing solutions according to the invention may be employed for magnetic purposes. They do not contain phosphorus or boron like the layers deposited by means of the known chemical metallizing solutions containing hypophosphite, boron hydride or borazane as reducing agents. The invention thus provides, in addition, an extension of the suitability of such layers for use, since in certain cases the presence of phosphorus or boron may be less desirable.

With physical metal salt developers it is known that the spontaneous formation of nuclei in the solution may be considerably reduced by adding a suitable surface-active ionic compound. The lifetime of the developer is thus prolonged to a high extent. The rate of development of the nuclei on the surface of the substrate is thus inhibited, but an image consisting of nuclei located slightly beneath the surface of the substrate is intensified at a reasonable rate to a satisfactorily adhering metal image. With the metallizing solutions according to the invention the addition of a suitable surface-active ionic substance also provides a prolongation of its potlife.

Suitable ionic surface-active compound are e.g., water soluble salts of primary alkylamines wherein the alkyl moiety is hydrophobic and contains at least eight carbon atoms, cetyl pyridinium halides, the methyl sulphate of monostearylamidoethylene-trimethyl:-amine, imidazolidine derivatives containing an alkyl of 16 carbon atoms attached to a carbon atom of the heterocyclic nucleus and a lower alkyl attached to a nitrogen of the heterocyclic nucleus, tolylundecylammonium compounds, benzyldimethyl (2(2 -[4(Cl,1,3,3- tetramethylbutyl) tolyloxyl] -ethoxy)ethyl) ammonium compounds, N-lauryl(aminosulpho) B-aminobutyric acid, trimethyl-2-oleoylamino-ethyl ammonium compounds, trimethyl-2-stearyamino-ethyl ammonium compounds and morpholine compounds of the formula wherein R is alkyl of 16 to 24 carbon atoms, alkylarylsulfonates and sulfonat ed alkyl alcohols.

lna preferred embodiment a metallizing solution for the production of lead and/or tin layers contains l-"b and/or Sn ions and as a redox mixture V and V ions.

A metallizing solution for the production of nickel, cobalt or indium layers contains from the salt of one or more of these metals as a redox mixture: Cr and Cr"' ions.

A special variant of a metallizing solution according to the invention is formed by a known chemical metallizing solution for depositing copper, nickel and/or cobalt, to which are added, apart from the conventional reducing agent, suitable reducing ions according to the invention. These conventional reducing agents may be selected from formaldehyde, hydrazine and aldehyde-sugars for copper and alkalihypophosphite, borazanes and boron hydrides for nickel and/or cobalt. This addition has the effect that the preliminary activation of the image of metal nuclei, which is otherwise required with the use of these known solutions, may be dispensed with. After a time the metal deposition is obtained mainly by the first-mentioned reducing agent, with the same rate as with a previously activated latent image in a similar solution without the reducing ions according to the invention.

The metallizing solutions according to the invention may, of course, also be employed for intensifying layers with a uniform distribution of metal nuclei, that is to say for a uniform metallization and images consisting of nuclei metal preliminarily intensified in known manner to a greater or lesser extent.

Since the metallizing solutions according to the invention are likely to be oxidized in air, they have to be used in a nonoxidizing, that is to say in an inert or slightly reducing atmosphere.

The invention will now be explained with reference to a few examples.

1. A cellulose triacetate foil, saponified to a depth of 2 pm, was sensitized by impregnating it for 2 minutes in an aqueous solution containing per liter:

0.4 mol of sodium salt of p-methoxybenzene diazosulphonic acid,

0.1 mol of Cd lactate, 0.1 mol of Ca lactate and 0.1 mol of lactic acid.

A strip of this foil was exposed behind a line negative having parallel lines of a width of 50 pm. and a pitch of H10 um. to the light of a high-pressure mercury vapor lamp of l25-W (type HPW) at a distance of cm. for 20 seconds. Subsequently, the strip was treated for 4 seconds with an aqueous solution containing per liter:

0.005 mol of mercurous nitrate, 0.0l mol of silver nitrate and 0.01 mol of nitric acid. After washing in distilled water for a short time (15 seconds) the strip was treated for l minute with a 2 molar solution of Ca nitrate in water. The mercurous and silver ions absorbed at the cellulose, which ions may give rise to fogging, were thus substituted for by calcium ions. Then the strip was again washed in distilled water for a short time, after which the latent image consisting of silver amalgam nuclei was intensified for 10 minutes in a nitrogen atmosphere by means of a solution obtained by mixing:

2 parts by volume of an aqueous solution of 50 percent by weight of tin borofluoride, v 0.8 part by volume of an aqueous solution of 0.5 percent by weight of Armac 12 D and 0.5 percent by weight of Lissapol N,

5.2 parts by volume of oxygen-free water and 2 parts by volume of a V */V* -containing solution, which was prepared as follows:

12.65 g. of vanadyl sulphate was dissolved in 25 ml. of oxygen-free water; After the addition of l0 ml. of 10 N sulphuric acid, the solution was diluted with oxygen-free water to a volume of 50 ml. While nitrogen was passed through (at least 0.3 liter/minute), the solution was shaken on ashaking machine for 30 to 45 minutes with zinc amalgam. The latter was produced by adding 6.5 g. of zinc powder and a few ml. of 0.5 N sulphuric acid to 50 g. of mercury. The formation of the amalgam was promoted by slight heating. After cooling the amalgam was washed with distilled water.

The final intensifying solution was about 0.9 N of V and about 0.1 N in W. AE of the solution was about 200 mv. Armac 12 D" is a cation-active substance, i.e., predominantly dodecylaminlacetate and Lissapol N is a nonionic surface-active substance, i.e., an alkylated phenol condensated with ethylene oxide.

The resultant pattern of the tin lines on the substrate could be rendered highly bright by softly rubbing with a flannel towel. Within a narrow temperature range the lines were superconductive. The transitional temperature was approximately equal to that of pure metallic tin.

The stability of the intensifying solution was at least 1 hour. A corresponding solution without the addition of stabilizing surface-active substances was deteriorated by spontaneous formation of nuclei within 1 minute.

2. Tin electrodes were applied in the following manner to CdS- and CdSe-wafers for photocells. The wafers were coated by dipping with a light-sensitive Kalle Kopierlack." After drying of the lacquer layer, they were exposed behind a negative of the ml. electrode pattern for 5 minutes to a high-pressure mercury-vapor lamp of W (type HPR) at a distance of 30 cm. After the exposed layers were removed by means of 7 an alkali solution the CdS was again accessible at the areas where the electrodes had to be applied. These areas were then sensitized by treating the wafers in order of succession with a solution obtained by dissolving l g. of stannous chloride in l ml. of concentrated hydrochloric acid, the solution being diluted with water to 100 ml. (time of treatment 2 minutes) and with an aqueous solution containing per liter:

0.01 mol of palladium (ll) chloride,

1 mol of potassium chloride and 0.01 mol of hydrochloric acid (time of treatment also 2 minutes).

In the interval between the treatments and after the last treatment the wafers were thoroughly washed in water.

The sensitized areas were subsequently intensified by means of a solution obtained by mixing:

2 parts by volume of an aqueous solution of 50 percent by weight of tin borofluon'de,

0.8 part by volume of an aqueous solution of 0.5 percent by weight of Armac 12 D and 0.5 percent by weight of Lissapol N 5.2 parts by volume of oxygen-free water and 2 parts by volume of a Cr /Cr -containing solution, which was prepared as follows:

To 100 ml. of a l.5-molar solution of chromic chloride in water, containing in addition 1 mol of hydrochloric acid per liter, was added 56.5 g. of zinc amalgam. The latter was produced in the manner described in example 1. The mixture was shaken, while nitrogen was passed through, for 2 hours ona shaking machine. The ratio of concentrations Cr /Cr in the shaken mixture was 1.

The intensification was continued for minutes in a nitrogen atmosphere. AE of the intensifying solution was about 200 mv. After washing in water the unexposed Kopierlack" was removed by means of acetone. The wafers had sharply defined tin electrodes, adhering firmly to the CdS.

3. An exposed strip of the foil of example 1 was provided in the manner described in example l with an image consisting of silver amalgam nuclei, after which, like in example 1, the adsorption-exchange treatment was carried out. After washing in distilled water the image of nuclei was intensified for 15 minutes in a nitrogen atmosphere with the aid of a solution produced by mixing:

0.4 part by volume of a l-molar lead acetate solution in water, 1.6 parts by volume of an aqueous solution of 1 percent by weight ofArmac 12 D,

0.8 part by volume of an aqueous solution of 1 percent by weight of Lissapol N,

6 parts by volume of oxygen-free water,

2 parts by volume of the Cr ICr -containing solution of example 2.

After washing in water, drying and softly rubbing the lead image with a flannel towel a conductive line pattern was obtained.

4. Light-sensitive material as described in example i was exposed stepwise to a high-pressure mercury-vapor lamp. The introduction of the nuclei and the exchange of the adsorbed parts were carried out as in example 1. The intensification was carried out by a IO-minute-treatment in a nitrogen atmosphere with a solution obtained by mixing:

1 part by volume of a l-molar lead acetate solution in water, 0.4 part by volume of an aqueous solution of 1 percent by weight ofArmac 12 D,

0.4 part by volume of an aqueous solution of 1 percent by weight of Lissapol N,"

4 parts by volume of a V /V -containing solution, which was produced as follows:

On the basis of the sulphuric acid vanadyl sulphate solution of example 1 the sulphate was completely precipitated by means of a barium acetate solution in the form of barium sulphate. After filtering off the precipitate the solution was 0.4 molar in the vanadyl compound. Fifty milliliters of this solution were reduced on a shaking machine, while nitrogen was passed through, with 22.6 g. of zinc amalgam. Neutral grey, internal lead images, lying beneath the surface of the substrate were obtained.

5. A strip of the light-sensitive foil of example I was exposed for 15 seconds behind a negative to a HPW lamp of 125 W at a distance of 30 cm. After the formation of the latent image consisting of silver-amalgam nuclei (see example I and washing with distilled water, nickel intensification was carried out by a l.5-hour-treatment in a nitrogen atmosphere with a solution obtained by mixing:

4 parts by volume of an aqueous 4-molar solution of nickel chloride,

1 part by volume of an aqueous solution of 1 percent by weight ofArmac [2 D,"

0.4 part by volume of an aqueous solution of l percent by weight of Lissapol N,"

0.6 part by volume of oxygen-free water and 4 parts by volume of the Cr /Cr -containing solution of example 2. Electrically conductive, magnetic nickel patterns were obtained.

6. A polyester foil was provided with an adhesive layer by pouring on a solution of:

1.4 g. of Hycar 1041 (a butadiene acrylonitrile copolymer), 0.6 g. of alkaline cresol resin,

8 g. of methylethylketone and g. of methylisobutylketone,

which solution was caused to drip off.

After drying at room temperature a light-sensitive layer was applied to the adhesive layer by pouring on an aqueous solution containing per liter:

0.1 mol of sodium salt of o-methoxy-benzenediazosulphonic acid,

0.05 mol of Cd lactate,

0.05 mol of Ca lactate,

0.05 mol of lactic acid and 10 g. ofLissapol N.

After the excess quantity of the light-sensitive solution had been caused to drip off and after drying of the remaining layer, the pattern was exposed for 30 seconds to a l25-W HPR lamp at a distance of 30 cm. The image of nucleiwas formed by means of an aqueous solution containing per liter:

0.05 mol of mercurous nitrate, 0.01 mol of silver nitrate and 0.1 mol of nitric acid.

After washing in distilled water, the latent image was intensified with nickel by treating it for 10 minutes in a nitrogen atmosphere with a solution obtained by mixing: 6 parts by volume of a 4-molar aqueous solution of nickel chloride and 8 parts by volume of the Cr /Cr -containing solution of example 2, so that electrically conductive, magnetic nickel patterns were obtained.

7. A cellulose triacetate foil, saponificd to a depth of 6 am, was sensitized by impregnating it for 2 minutes in an aqueous solution, containing per liter:

0.15 mol of Na salt of p-methoxybenzenediazosulphonic acid, 0.1 mol of Cd lactate,

0.1 mol of Ca lactate and 0.1 mol of lactic acid.

A strip of this foil was exposed behind a line negative for 10 seconds to a l25-W HPR lamp at a distance of 40 cm. The formation of the image of nuclei and the exchange of the absorbed ions were carried out as described in example I. Finally the latent image was intensified to an electrically conductive, magnetic cobalt pattern by keeping it for 17 hours in a nitrogen atmosphere in a solution obtained by mixing 4 parts by volume of a 3-molar aqueous solution of cobalt chloride,

1 part by volume of an aqueous solution of 1 percent by weight ofArmac 12 D,"

0.4 part by volume of an aqueous solution of 1 percent by weight of Lissapol N,

0.6 part by volume of oxygen-free water and 4 parts by volume of the Cr lCr containing solution of example 2. I

A further strip of the same light-sensitive foil, provided in a similar manner with a nuclei image, was intensified to an electn'cally conductive indium pattern by treating it for l hour in a nitrogen atmosphere with a solution obtained by mixing:

2 parts by volume of a l-molar aqueous solution of indium sulphate,

0.4 part by volume of an aqueous solution of 1 percent by weight ofArmac 12 D,

0.2 part by volume of an aqueous solution of 1 percent by weight ofLissapol N,

3.4 parts by volume of oxygen-free water and g 4 parts by volume of the Cr /Cr -containing solution of example 2.

8. The following, weakly active intensifying solutions were employed for the production of internal, nonconductive copper images on the basis of images consisting of silver amalgam nuclei obtained as described in example I 1 part by volume of a l-molar aqueous solution of copper sulphate,

0.5 part by volume of an aqueous solution of 1 percent by weight of Armac l2 D,

0.5 part by volume of an aqueous solution of 1 percent by weight of Lissapol N,

4 parts by volume of a predominantly Ti/Ti-containing solution, produced as follows:

1.6 g. of titanyl sulphate was dissolved in 10 ml. of 10 N sulphuric acid, after the solution was diluted with 90 ml. of oxygen-free water. This solution was shaken for 30 minutes on a shaking machine, while nitrogen was passed through, with 56.5 g. of zinc amalgam (see example l). AE of the intensifying solution was about 230 0.3 part by volume of a l-molar aqueous solution of copper sulphate and 10 parts by volume of a V /V -containing solution, obtained by mixing:

4 parts by volume of the V flv containing solution of example l,

L5 parts by volume of N sulphuric acid,

28.5 parts by volume of oxygen-free water and 10 parts by volume of a 0.4 N solution of potassium dichromate in water.

AE of this intensifying solution was about 60 mv.

9. An image consisting of silver amalgam nuclei, obtained in the manner described in example 1, was intensified for 50 minutes in a nitrogen atmosphere to a neutral-grey, internal copper image, by means of an intensifying solution obtained by mixing:

2 parts by volume of an aqueous solution containing per liter:

0.20 mol of copper sulphate,

0.25 mol of triethanolamine and 0.24 mol of tetrasodium salt of ethylene diamine tetracetic acid,

3 parts by volume of a 4.5-rnolar aqueous solution of ammonia, 0.25 part by volume of a 2.5-molar aqueous solution of sodium hydroxide, 8 parts by volume of an aqueous oxygen-free solution, containing per liter: 1

0.09 mol of ferrous sulphate, 0.25 mol of triethanolamine and 0.24 mol of tetrasodium salt of ethylene diamine tetraacetic acid, AE of the intensifying solution was about l 40 mv.

After a stay of about 10 minutes in this solution the latent image was sufficiently intensified to be intensified rapidly further by means of a known electroless copper-plating solution, for example, a solution containing per liter:

0.14 mol of copper sulphate,

0.30 mol of tetra-sodium salt of ethylene-diamine tetraacetic acid, 0.65 mol of sodium hydroxide and ml. of formaline (about 40 percent by weight). By adding 2 parts by volume of formaline (40 percent by weight) to said intensifying solution the copper deposition could be accelerated. In this way electrically conductive copger images were obtained.

. When a substrate provided with a latent image obtained in the manner described in example 1, subsequent to the exchange of the adsorbed ions, was introduced in an electroless copper-plating solution obtained by mixing: 8 parts by volume of an aqueous solution containing per liter:

0.07 mol of copper sulphate, 0.24 mol of tetrasodium salt of ethylene-diaminetetraacetic acid, 0.32 mol of sodium hydroxide and 2 parts by volume of formalinelab out 40 percent by weight) no intensification could be found, even after a fairly long stay. However, if in addition 0.25 part by volume of an aqueous, oxygen-free solution was added which contained per liter: 0.09 mol of ferrous sulphate and 0.48 mol of tetrasodium salt of ethylene-diaminetetraacetic acid, and if the mixed solution was used in a nitrogen atmosphere, a good conducting copper image was obtained already after l2 minutes. The electric conductivity in this case and in all other cases relating to electrically conductive metal pafi eins was largely sufficient for a further electroplating intensification of the pattern. The thickness of 'the co nductive l'a'yersg varied in these embodiments between a few tenths urnQand afew What is claimed is: a l 1 l. A method of selectivelyf metallizing an atfleastfsuperficially electrically nonconductive' support, said method comprising the steps, photographlcally forming a'tiietai'muclei image on said support of a metal selected from the group consisting of silver, mercury and silver amalgam and treating said metal nuclei image, in a nonoxidizing atrnospl'lere', with a metallizing composition suitable for depositing a metal selected from the group consisting of eopper,'tin, nickel, lead, cobalt and indium, said composition consisting essentially of an aqueous solution of ions of a metal selected from the group consisting of copper, tin, nickel, lead, cobalt and indium and, as essentially the sole means for causing said deposition, a reversible mixture of at least one reducing ion selected from the group consisting of Fe, V, V, Ti, Ti, Cr and Eu and their oxidized ions, the concentration of the ions being such that the difference between the potential of the metal to be deposited with respect to its ions and the oxidation-reduction potential of the mixture of the reducing ion and its oxidized ion is at least 50 mv.

2. The method of claim 1 wherein the aqueous solution contains in addition an ionic surface'active compound.

3. The method of claim 2 wherein a metal deposited from the solution is selected from the group consisting of lead and tin and the solution contains a mixture of V and V ions.

4. A metal pattern obtained by the method of claim I.

1x23 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 537 385 1 69 Dated ,j f QmLZE 1972 Inventor(S) WILLEM GERBRECH'I' DE RUIG ET AL It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

fi In the title page, after [21] Appl. No: 635,409" there should be inserted:

"Foreign Application Priority Data May 7, 1966 Netherlands. 6,606,262".

In the title page, item 72, after "Tromplaan" there should be inserted:

"Oegstgeest.

Signed and sealed this 6th day of February 1973'.

(SEAL) Attest:

EDWARD M. PLETCIII-IR,JR. ROBERT OOTTSCHALK Attesting Officer Commissloner of Patents 

2. The method of claim 1 wherein the aqueous solution contains in addition an ionic surface-active compound.
 3. The method of claim 2 wherein a metal deposited from the solution is selected from the group consisting of lead and tin and the solution contains a mixture of V2 and V3 ions.
 4. A metal pattern obtained by the method of claim
 1. 